[Feature proposal] Distinguishing between error strings and error numbers

[ehmicky]

At the moment result.code is either a string like EACCES, an integer like 13 or undefined.

It would be nice to split this property into two: code for the string and errno for the integer.

This would be a breaking change if the name code is re-used. Otherwise we can pick another property name.

If this sounds good, I will submit a PR.

[sindresorhus]

Ah yeah... I should not have reused .code for something different.

I don't want to do a breaking change just for this, so I suggest we add a .exitCode property. I prefer that over .errno. .errno in Node.js can be both a string and a number.

And in the next major version, we stop putting the exit code on the .code property.

[ehmicky]

Sounds good.

So code is currently either string or integer. Should exitCode be string? Which property name should be for integer?

[sindresorhus]

.exitCode should be an integer. The exit code the process excited with.

[ehmicky]

Since code can be either a string or an integer, should there a third property that can only be a string?

[sindresorhus]

What would it contain? Example?

[ehmicky]

For example code currently can be either a string ("EACCES"), a positive integer (13) or undefined.
exitCode will only be a positive integer (13) or undefined.
A third property could be only a string ("EACCES") or undefined.

[sindresorhus]

A third property could be only a string ("EACCES") or undefined.

Do you have any use-case for this? You could mostly compare .code to something anyway, in which the type doesn't matter.

[ehmicky]

The use case would be if a user wants to print the signal name but not number. Some users might consider that more user-friendly. Also signal names are cross-platform, whereas signal numbers aren't.

[sindresorhus]

Alright, any suggestion on what to name this string-only property?

[ehmicky]

code (integer or string), exitCode (integer), exitName (string)?
Or code (integer or string), codeNumber (integer), codeName (string)?

[sindresorhus]

I think it should be exitCode for the number, since that's what it's called outside the Node.js ecosystem too. As for the string, maybe exitCodeName or exitCodeId?

[ehmicky]

code (integer or string), exitCode (integer), exitCodeName (string) sounds good, I can open a PR.

Should code be marked as deprecated and removed in next major release or not? Users will be able to do exitCodeName || exitCode if they want. Otherwise having a single type might be better for them.

[sindresorhus]

code (integer or string), exitCode (integer), exitCodeName (string) sounds good, I can open a PR.

👍

Should code be marked as deprecated and removed in next major release or not?

No, I think it should stay, since users are used to it from Node.js core errors.

[ehmicky]

PR at #187